Essential activation of PKC-delta in opioid-initiated cardioprotection

Stimulation of the delta (1)-opioid receptor confers cardioprotection to th e ischemic myocardium. We examined the role of protein kinase C (PKC) after delta -opioid receptor stimulation with TAN-67 or D-Ala(2)-D-Leu(5)-enkeph alin (DADLE) in a rat model of myocardial infarction induced by a 30-min co ronary artery occlusion and 2-h reperfusion. Infarct size (IS) was determin ed by tetrazolium staining and expressed as a percentage of the area at ris k (IS/AAR). Control animals, subjected to ischemia and reperfusion, had an IS/AAR of 59.9 +/- 1.8. DADLE and TAN-67 administered before ischemia signi ficantly reduced IS/AAR (36.9 +/- 3.9 and 36.7 +/- 4.7, respectively). The delta (1)-selective opioid antagonist 7-benzylidenenaltrexone (BNTX) abolis hed TAN-67-induced cardioprotection (54.4 +/- 1.3). Treatment with the PKC antagonist chelerythrine completely abolished DADLE- (61.8 +/- 3.2) and TAN -67-induced cardioprotection (55.4 +/- 4.0). Similarly, the PKC antagonist GF 109203X completely abolished TAN-67-induced cardioprotection (54.6 +/- 6 .6). Immunofluorescent staining with antibodies directed against specific P KC isoforms was performed in myocardial biopsies obtained after 15 min of t reatment with saline, chelerythrine, BNTX, or TAN-67 and chelerythrine or B NTX in the presence of TAN-67. TAN-67 induced the translocation of PKC-alph a to the sarcolemma, PKC-beta (1) to the nucleus, PKC-delta to the mitochon dria, and PKC-epsilon to the intercalated disk and mitochondria. PKC transl ocation was abolished by chelerythrine and BNTX in TAN-67-treated rats. To more closely examine the role of these isoforms in cardioprotection, we uti lized the PKC-delta selective antagonist rottlerin. Rottlerin abolished opi oid-induced cardioprotection (48.9 +/- 4.8) and PKC-delta translocation wit hout affecting the translocation of PKC-alpha,- beta (1), or -epsilon. Thes e results suggest that PKC-delta is a key second messenger in the cardiopro tective effects of delta (1)-opioid receptor stimulation in rats.